Power amplifiers are often used to boost, or amplify, the power of a radio frequency (RF) signal having a relatively low power. Thereafter, the amplified RF signal can be used for a variety of purposes, including driving the antenna of a RF transmitter. As such, power amplifiers are often included in devices, such as, mobile phones to amplify a RF signal for transmission. For example, in devices supporting Global System for Mobile Communications (GSM) (or 2G devices), wideband code division multiple access (W-CDMA) (or 3G devices) and/or Long Term Evolution Advanced (LTE-A) (or 4G devices), a power amplifier is often used for RF signal amplification.
It may be beneficial to manage the amplification of RF signals because the desired transmit power level can vary in dependence on a number of factors including the distance between the user and a base station and/or the mobile environment. In mobile devices, in particular, the power consumption of a power amplifier can be an important consideration. One technique for reducing power consumption of a power amplifier is envelope tracking (ET), in which the voltage level of the power supply of the power amplifier is varied or controlled in relation to the envelope of the RF signal. Thus, when the envelope of the RF signal increases, the voltage supplied to the power amplifier is also increased. Likewise, when the envelope of the RF signal decreases, the voltage supplied to the power amplifier is decreased, thereby to reduce power consumption.